[bloak]

This is interesting! But how does a dense crowd of people compare to a queue of lorries carrying cement or building materials in terms of mass per square metre?

Let's try to find some data ... ... ... A fully loaded Hanson cement lorry seems to be 32 tonnes / 2.55 m / 9.15 m, which is about 1.4 tonnes per square metre. That corresponds to 20 x 70 kg people per square metre, which would be a disaster whether or not the floor gives way, unless it's a very special kind of crowd (acrobats or something).

[Denvercoder9]

Lots of roads and bridges have a limit on axle load permitted on them. You can't do that with pedestrian bridges.